If you’re concerned about the effects of radiation exposure from mammograms, medical tests, airport scanners or cell phones, here’s help. Lifescript’s Health Detective reveals the truth behind the types of radiation you face every day…

Just about everything around us – the ground, sky, your microwave, even the person you sleep next to at night – constantly emits small amounts of radiation.

So does that mean we should all get fitted for lead suits?

Not by a long shot, experts say.

“The average amount [of radiation] we get per year is not damaging,” says radiological physicist David Schauer, Sc.D., executive director of the National Council on Radiation Protection and Measurement, a nonprofit organization that researches the subject.

“We’re exposed to it every day and we’re still here,” he says. “It’s a big part of living on Earth.”

Our bodies are adept at repairing damage from radiation all the time, and it takes years – sometimes decades – for even large amounts of radiation to trigger cancerous changes. Here’s why:

Scientists divide radiation, which is simply a form of energy, into two kinds:

Non-ionizing radiation, which includes radio waves, is low in frequency and not strong enough to hurt you.

Ionizing radiation,whichis produced by unstable atoms and has enough energy to damage DNA. But the amount, often counted in millirems (or mrem), makes a huge difference in health. (A millirem is 1/1000th of a rem, the main unit used to measure radiation absorption.)

Each year, 300-350 mrem is the average amount of radiation we’re exposed to. Known as “background radiation,” this is what’s emitted by outer space (where the sun and other stars constantly create charged atomic particles called cosmic rays), the earth’s crust, and even our own bodies, according to the U.S. Nuclear Regulatory Commission (NRC). It’s far below levels of radiation considered harmful.

“You can’t do anything about that exposure,” says Jennifer Johnson, M.S., radiation health physicist for the University of Washington Medical Center in Seattle. “[But] it really is nothing to worry about.”

Even radiation from Japan’s nuclear power-plant disaster drifting overseas is nothing to fear, experts say. By the time it reached the U.S., it had become so dispersed that it never even raised the normal levels of background radiation, according to the Environmental Protection Agency (EPA). And now the levels are dropping even further, the EPA says.

But some lifestyle choices can raise your average annual exposure slightly above “background” levels. Smoking, for example, adds more than 200 mrem per year. A cross-country airline flight exposes you to an extra 5 mrem, because flying brings you closer to cosmic radiation.

The average extra yearly dose for airline workers is 219 mrem, according to the Health Physics Society (HPS), an organization of radiation scientists. But that falls well within the Federal Aviation Administration’s recommended occupational limit of 2,000 mrem per year.

Less than 10,000 mrem is still an acceptable dose and won’t cause immediate harm to your organs, experts say. The effects, if any, wouldn’t be observed for 5-20 years after exposure. For every 10,000 people who absorb an extra 1,000 mrem in a single exposure (from certain medical tests, for example), only about five or six more are likely to die of cancer, according to EPA estimates.

More than 10,000 mrem, absorbed all at once, is potentially harmful and could increase your lifetime risk of cancer. Radiation exposure greater than that amount would be unusual – possibly from radiation therapies or proximity to a nuclear accident.

Under normal circumstances, could you get enough radiation to raise your own lifetime cancer risk? It’s unlikely, but possible.

Radiation SourcesThe Medical Detective looked into the five radiation controversies women are most worried about these days to get to the truth about what’s really dangerous.

1. Natural RadonWhile most background radiation is too weak to be harmful, there’s a common source of radiation danger from the earth you should beware of: radon, an invisible radioactive gas responsible for thousands of lung cancer deaths each year.

The Medical Detective was surprised to learn that radon is the second-leading cause of lung cancer in the U.S., after smoking, according to the EPA.

It results from the natural breakdown of uranium in soil, rock and water, and becomes trapped in the air you breathe in buildings.

Of the 350 or so mrem of radiation the average person in the U.S. receives yearly, radon is responsible for about 200 mrem – or 55% of total exposure, according to the University of Michigan.

The radiation danger and your risk depend on where you live and the soil homes and offices are built on. About 1 out of 15 homes in the U.S., new or old, has elevated levels – often because it gets in through cracks and holes in the foundation.

The only way to find out if there’s radiation in your home is to test for it, starting at the building’s lowest point (such as the basement), where the concentration is greatest. The EPA has information about inexpensive test kits that cost $15-$25.

Take action if the radon in your home is above the EPA’s acceptable level (which is 5-10 times the average outdoor concentration), advises Schauer.

Radon reduction systems are up to 99% effective. Check with your state radon office for more information.

2. Cell phonesSince they’re glued to just about everyone’s ears, most people think mobile phones are safe. Yet scientists haven’t been able to rule out a link between heavy cell-phone use and cancer, especially a rare form of brain tumor.

Mobile phones operate by sending microwaves to and from local receivers. This is non-ionizing radiation, but it still can heat body tissue – including the brain – when you hold a phone to your ear.

The controversy has grown since May 2011, when a World Health Organization (WHO) panel of experts – which reviewed dozens of studies on potential radiation danger – issued a statement that the devices could “possibly” cause cancer.

Yet the link is far from proven. In 2010, the largest cell phone study to date – a 13-nation examination of tumor patients, called Interphone – found no relation between cell phone use and cancer risk.

For now, the wise path is more study, says Jonathan M. Samet, M.D., professor and Flora L. Thornton chair of the Department of Preventive Medicine at the University of Southern California’s Keck School of Medicine, who chaired the WHO research group.

“There will be more research, and hopefully more certain information [about radiation risk], in the future,” he tells the Medical Detective.

In the meantime, you can minimize any possible phone radiation danger by using the speaker option or a wireless headset.

If you’re worried, “the best thing to do is avoid putting a phone on [your] ear,” Samet says. “That delivers the greatest exposure to the brain.”

3. Medical tests Medical exams such as CT (computed tomography) scans, while relatively safe, do deliver some radiation to the body.

Since 1980, there has been a 20-fold increase in CT scanning and nuclear imaging (medical tests that require small amounts of radioactive “tracer” material to be injected into the body), according to the October 2010 issue of Harvard Women’s Health Watch.

“But our bodies are good at repairing small amounts of damage if they occur,” she says. “An X-ray or CT scan once a year usually isn’t enough to cause a huge problem.”

With medical tests, aim for exposure levels that are “as low as reasonably achievable” to get the results you need, says Schauer.

Pregnant women don’t need to worry about most diagnostic medical procedures – there’s little risk to a fetus when X-rays are taken of areas other than the abdomen, according to the HPS (Health Physics Society).

“You would have to be exposed to 500 chest X-rays before worrying about harm to a fetus,” says Charles J. Gomer, Ph.D., professor of pediatrics and radiation oncology at the University of Southern California Keck School of Medicine. “We can’t say there are no risks from diagnostic medical procedures, but they’re very, very low.”

Fetuses that receive a small amount of radiation – equal to 500 chest X-rays – don’t risk birth defects. But they have a 2% higher risk of cancer later in life, according to the federal Centers for Disease Control and Prevention (CDC).

Here are the exposure levels you’re likely to face from various procedures:

CT scans: If you’re worried about the effects of radiation exposure, be careful with CT scans, X-rays that reveal soft-tissue growths.

“CT scanning is a fantastic test, but it’s overused,” says Rebecca Smith-Bindman, M.D., professor of radiology and epidemiology at the University of California-San Francisco School of Medicine. “You have to think of the benefits outweighing the harm.”

Someone who has multiple CT scans or other diagnostic medical exams, especially close together, may have a higher lifetime risk of cancer than someone who doesn’t, a February 2011 study published in the Canadian Medical Association Journal found.

A 2007 New England Journal of Medicine articleagreed: The accumulated effects of 2-3 CT scans could provide as much as 9,000 mrem, enough to increase a patient’s cancer risk, it said.

Most of the time, the radiation danger from a CT scan is low, says Gomer. Still, check with your physician to see if you really need the test. Another diagnostic tool may work as well.

Mammograms: This X-ray of the breast exposes women to 70 mrem of radiation.

But by the time women are old enough to need mammography, there’s very little potential danger, according to Johnson. Breast tissue in women over age 40 is less sensitive to radiation because it’s no longer growing rapidly, she says.

“The benefit of being able to diagnose cancer early through mammogram far outweighs the potential risk, which is minuscule,” Gomer says.

X-rays: Your sensitivity to X-rays depends on which tissues and body organs are exposed. Chest X-rays emit 8 mrem, dental X-rays give off 10, head and neck X-rays have 20, and lumbar spinal X-rays have 130.

“The diagnostic dose of radiation might [lead to] a tiny increase in the cancer rate,” Gomer says. “But the risks are so low in the general population, you shouldn’t be concerned.”

4. Airport security scannersGet used to these devices, which use reflected radiation to take images of travelers’ bodies and anything they might be carrying. Hundreds are operating in U.S. airports, and 1,000 are expected by the end of the year – when two out of three passengers will pass through the machines.

About half of the scanners are millimeter-wave machines; they emit a radio frequency, which is non-ionizing radiation. No one’s suggesting these could be hazardous.

The other half is so-called backscatter scanners, which use low-energy X-rays. (While millimeter-wave machines look like a phone booth with clear walls, backscatter machines look like two boxes that you stand between.)

Do backscatter machines pose a radiation danger to passengers?

“You get more radiation high in the air on a jet than from these machines,” Smith-Bindman says.

Nevertheless, some scientists are waving red flags because the beam doesn’t enter the body, so most of the radiation is delivered to the skin. They advocate more testing to find out how much radiation the skin receives.

Most estimates, from the government and independent radiation scientists, say the amount is extremely low. A traveler would have to go through 50 scans to get the amount of radiation in a dental X-ray, according to Smith-Bindman.

USC’s Gomer agrees, saying that most of the “backscatter” energy is reflected back into the machines.

“The doses and types of radiation shouldn’t be a concern to the public,” he says.

Microwaves are a form of electromagnetic, non-ionizing radiation, according to the EPA. They’re reflected by metal, pass through glass, paper and plastic, and are safely absorbed by food.

If you were exposed to large amounts of microwave radiation – much more than you would ever get from your home oven – you could experience heat injury, says the EPA.

Newer ovens are unlikely to leak radiation, but if one does – usually due to a damaged door – it’s hard to detect. To be safe, the Food and Drug Administration (FDA) recommends that you don’t stand directly in front of or up against the oven while it’s operating.

Even then, the allowable leakage is far below levels that could do harm, according to the HPS.

“Manufacturers have to meet standards,” Schauer says. “That industry is on solid ground.”

The Bottom LineWhen it comes to deciding how much exposure to radiation you’re willing to absorb, always remember to “think in a logical way about the benefit outweighing the harm,” Smith-Bindman says.

“Discuss it with your doctor, and make a decision based on your best interest.”

Will You See Your 80th Birthday?What is your life expectancy? Can you rely on good genetics to keep you thriving through the years, or do you need to do more to raise your odds of living longer? Find out your chances of making it to age 80 in this life-expectancy quiz.

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